Gas and/or vapor discharge lamp having a u-shaped discharge tube

ABSTRACT

The invention relates to the concentration of a U-shaped discharge tube in an outer envelope namely at the bend of this tube. The invention provides a centering member which includes a rectangular support of leaf spring, the inner wall of this support closely surrounding the two legs of the discharge tube. When using the invention the risk of cracking of the discharge tube is only small. FIG. 2.

United States Patent Goossens 1 June 6, 1972 [54] GAS AND/OR VAPOR DISCHARGE [56] References Cited LAMP HAVING A U-SHAPED FOREIGN PATENTS OR APPLICATIONS DISCHARGE TUBE 235,344 8/1961 Australia ..3l3/220 [72] Paul Marguerite 790,710 7/1968 Canada..... ..-.313 220 Waasmunster, Belgium [73] Assignee: U.S. Philips Corporation, New York, NY. A Primary Examiner-John Kominski Filed: Feb. 18 1971 Attorney-Frank R. Trifan [21] App]. No.: 116,435 [57] ABSTRACT The invention relates to the concentration of a U-shaped [30] Foreign Appli tion Prio ity D 18 discharge tube in an outer envelope namely at the bend of this Feb. 25, 1970 Germany ..G 70 06 868.7 tuba The invention provides a centering member which includes a [52] U.S. Cl ..313/220, 313/253, 3 13/292 rectangular support f l f spring the inner wall f this [51] Int. Cl. ..H01 61/34 port closely surrounding the two legs f the discharge tube. [58] Field of Search ..313/220, 253, 292

When using the invention the risk of cracking of the discharge tube is only small. FIG. 2.

4 Claims, 3 Drawing Figures I I 5 2Q 6 i 3 4 1 I y ii" 21 I 4.. l 7

22 H 24 1 I l 21 GAS AND/OR VAPOR DISCHARGE LAIVIP HAVING A U- SHAPED DISCHARGE TUBE The invention relates to a gas and/or vapor discharge lamp,particularly a low-pressure sodium vapor discharge lamp, having a U-shaped discharge tube and an outer envelope encompassing this tube, a centring member of the discharge tube consisting of mainly leaf spring being present near the bend of this discharge tube, which centring member has two U-shaped parts whose legs remote from the tube merge into a bend connecting these legs and whose legs facing the tube are connected together through a'connectin'g piece being located partly at right angles to said legs.

A known discharge lamp of the above-mentioned kind is described, for example, in French Pat. No. 1.428.297. In this known lamp the centring member is provided with two additional metal projections which are located at right angles to the plane of the said U-shaped parts of the centring member. Some parts of these projections located between the legs of the discharge tube have only a small contact surface with the discharge tube. The latter is a drawback because as a result thereof cracking of the material of the discharge tube, which is generally made of glass, may occur comparatively soon. Such cracking may result from mechanical influences only. It is also possible that cracking results from, for example, sodium ions which penetrate the glass envelope of the discharge tube.

An object of the present invention is to provide a centring member for a U-shaped discharge tube in which cracking of said tube does not occur so soon.

A gas and/or vapor discharge lamp, in particular a low-pressure sodium vapor discharge lamp, according to the invention, having a U-shaped discharge tube and an outer envelope encompassing said tube, a centring member of the discharge tube consisting of mainly leaf spring being present near the bend of said discharge tube, which centering member has two U-shaped parts whose legs remote from the tube merge into a bend connecting said legs and whose legs facing the tube are connected together through a connecting piece being located partly at right angles to said legs, is characterized in that a support tube having a rectangular cross-section and consisting of leaf spring is provided between the last-mentioned legs of the centring member, the inner wall of the support tube closely surrounding the two legs of the U-shaped discharge tube.

An advantage of this lamp according to the invention is that cracking of the discharge tube occurs less rapidly because the additional part of the centring member is now formed as a sup port tube closely surrounding the two legs of the discharge tube. The contact surface between tube and cylinder is then larger than the surface for the case where the projections in the known lamp are used.

In a preferred embodiment of a lamp according to the invention in which the discharge tube has a sealing tip at its bend, the connecting piece of the legs of the U-shaped parts of the centring member facing the tube is a part four times bent rectangularly which surrounds the sealing tip on three sides.

An advantage of this preferred embodiment is that the sealing tip is also protected.

In a further preferred embodiment the outer side of each of the two short sides of the rectangular support tube has a resilient supporting member facing the outer envelope.

These resilient supporting members may be lead to a better 1 resilience of the discharge tube relative to the outer envelope. In the inoperative condition of the lamp it is not necessary for the resilient supporting members to engage the inner side of the outer envelope. In this inoperative condition the distance may be short, for example, a few mms.

In a special embodiment of a discharge lamp according to the invention the centring member is provided with a heatreflecting shield. This shield may be secured in a simple manner to the connecting piece which connects the legs of the centring member facing the discharge tube.

In order that the invention may be readily carried into effect, an embodiment thereof will now be described in detail, by way of example with reference to the accompanying diagrammatic drawing, in which FIG. 1 is a perspective view of a centring member of a lamp according to the invention;

FIG. 2 is a longitudinal cross-section and partly a plan view of a lamp according to the invention including a centring member according to FIG. 1 (FIG. 2 consists of two parts, the intermediate part of the lamp is omitted);

FIG. 3 is a longitudinal cross-section and partly a plan view of a part of the same lamp as the one shown in FIG. 2, but in a plane which constitutes an angle of 90 with the plane of intersection of FIG. 2. FIG. 3 is only a longitudinal cross-section of one lamp end.

In FIG. 1, the reference numerals l and 2 denote the legs of a U-shaped part of a centring member. The reference numerals 3 and 4 denote the legs of another U-shaped part of this centring member. A bend 5 connects the parts I and 4. A capshaped connecting piece 6 connects the legs 2 and 3. A sup- I port tube 7 with a rectangular cross-section is provided between the legs 2 and 3. Supporting springs 8 and 9 are provided on the exterior of the narrow sides of this support tube 7. The entire centring member of FIG. 1 is made of leafspring. In one embodiment this was chrome-nickel steel having a width of 7.5 ms and a thickness of approximately 0.5 mm.

In FIG. 2 the reference numeral 20 denotes a low-pressure sodium vapor discharge lamp provided with an outer envelope 21 and a discharge tube 22. This tube 22 is U-shaped (see FIG. 3). In FIG. 2 the reference numeral 23 denotes a lamp cap. The reference numeral 24 denotes an electrode which is provided in one end of the leg of the tube 22 facing the lamp cap 23. A second electrode (not visible in FIG. 2) which is present in the end of the other leg of the tube 22 is provided behind the electrode 24.

The centring member is provided in the lamp (see FIG. 2) namely at the end of this lamp remote from the lamp cap 23. The reference numerals of this centring member in FIG. 2 and also in FIG. 3 are the same as those in FIG. 1. A sealing tip of the tube 22 is denoted by the reference numeral 25. The sealing tip 25 is provided on the bend 26 of the discharge tube 22.

The legs 1 and 4 and the bend 5 of the centring member are located against the interior of the end part of the outer envelope 21. The springs 8 and 9 engage the interior of the outer envelope 21 also in this embodiment. The sealing tip is surrounded by the connecting piece 6 which is four times bent rectangularly. The two legs of the discharge tube 22 protrude through the support tube 7 of the centring member.

In one embodiment the lamp 20 was a lamp of approximately 180 watts having a length of approximately 110cm. The centring member (FIG. 1) was approximately 9 cm long and has a width distance leg l-leg 4) of more than 6 cm.

A possible centration of those ends of the U-shaped tube 22 which are provided near the electrode 24 (see FIG. 2) is not further shown in the Figure. A centration of these ends (near the electrode 24) may be effected, for example, with the aid of a centring member as described in United Kingdom Pat. No. 1,170,874.

If desired a circular heat-reflecting shield which is at right angles to the longitudinal axis of the lamp may be provided near the bend 26 of the discharge tube, for example, to maintain this bend 26 of the discharge tube 22 at a comparatively high temperature. Such a heat-reflecting shield (shown in a broken line in the Figures and denoted by the reference numeral 10) then includes, for example, a central aperture through which the portion of the connecting piece 6, bent around the sealing tip 25, protrudes.

The centration of the tube 22 shown in the upper parts of FIG. 2 and FIG. 3 gives only little risk of cracking of this tube.

What is claimed is:

1. A gas and/or vapor discharge lamp, particularly a lowpressure sodium vapor discharge lamp, having a U-shaped discharge tube and an outer envelope encompassing said tube, a centring member of the discharge tube consisting of mainly leaf spring being present near the bend of said discharge tube, which centring member has two U-shaped parts and whose legs remote from the tube merge into a bend connecting said legs and whose legs facing the tube are connected together through a connecting piece being located partly at right angles to said legs, characterized in that a support tube having a rectangular cross-section and consisting of leaf spring is provided between the last-mentioned legs of the centring member, the inner wall of the support tube closely surrounding the two legs of the U-shaped discharge tube.

2. A discharge lamp as claimed in claim 1, in which the discharge tube has a sealing tip at its bend, characterized in that the connecting piece of the legs of the U-shaped parts of the centring member facing the tube is a part four times bent 3. A discharge lamp as claimed in claim 1, characterized in that a resilient supporting member facing the outer envelope is provided on the exterior of each of the two short sides of the support tube.

4. A discharge lamp as claimedin claim 1, characterized in that a heat-reflecting shield is secured to the connecting piece which connects the legs of the centn'ng member facing the discharge tube. 

1. A gas and/or vapor discharge lamp, particularly a lowpressure sodium vapor discharge lamp, having a U-shaped discharge tube and an outer envelope encompassing said tube, a centring member of the discharge tube consisting of mainly leaf spring being present near the bend of said discharge tube, which centring member has two U-shaped parts and whose legs remote from the tube merge into a bend connecting said legs and whose legs facing the tube are connected together through a connecting piece being located partly at right angles to said legs, characterized in that a support tube having a rectangular cross-section and consisting of leaf spring is provided between the last-mentioned legs of the centring member, the inner wall of the support tube closely surrounding the two legs of the U-shaped discharge tube.
 2. A discharge lamp as claimed in claim 1, in which the discharge tube has a sealing tip at its bend, characterized in that the connecting piece of the legs of the U-shaped parts of the centring member facing the tube is a part four times bent rectangularly which surrounds the sealing tip on three sides.
 3. A discharge lamp as claimed in claim 1, characterized in that a resilient supporting member facing the outer envelope is provided on the exterior of each of the two short sides of the support tube.
 4. A discharge lamp as claimed in claim 1, characterized in that a heat-reflecting shield is secured to the connecting piece which connects the legs of the centring member facing the discharge tube. 